This application relates to a thermostat for use as a protective device in a scroll compressor, wherein the thermostat extends into a thermal well through an outer housing shell, and into the body of the non-orbiting scroll.
Scroll compressors are becoming widely utilized in refrigerant compression applications. In a scroll compressor, a pair of scroll members each has a base and a generally spiral wrap extending from the base. The wraps interfit to define compression chambers. One of the two scroll members is caused to orbit relative to the other, and as it does orbit, compression chambers defined between the spiral wraps are reduced in size to compress an entrapped refrigerant. An electric motor drives a shaft to in turn drive the orbiting scroll member through a coupling to cause the orbiting scroll member to orbit.
Various challenges arise with regard to the operation of a compressor, and in particular a scroll compressor. One challenge has to do with various operational problems that can raise the internal temperature in the sealed compressor housing.
Typically, a compressor includes a compressor pump unit mounted within a sealed housing the motor, and into compression chambers. Various problems can cause the temperature of the scroll set to reach undesirable levels, which will cause mechanical failures. As examples, if refrigerant has leaked from the refrigerant system such that there is too little refrigerant or if the evaporator fan fails, then the system condition will change and the compressor will see very high pressure ratios between discharge and suction. Compressing refrigerants to very high pressure ratios will generate unduly high temperature at discharge and also in the scroll itself.
For all of these reasons, thermal protection is typically included into a sealed compressor. Known types of thermal protection include a thermal shutoff switch associated with the motor. If the temperature of this switch becomes too high, it opens to stop operation of the compressor motor. Other types include the provision of thermostats in various locations within the sealed compressor housing. These have several downsides, including the fact that positioning the thermostat within the housing makes it difficult to communicate the thermostat to a system control outside of the compressor. Most of this prior art type thermostat connection communicates directly to the thermal protection switch at the compressor motor.
One proposed scroll compressor includes a thermostat extending through the wall of the housing and into a discharge chamber. However, the location of this thermostat does not necessarily receive adequate flow of refrigerant, and in particular at low volume flow times, such that it will shut down the system as quickly as would be desirable.